ADAS (Advanced Driver Assistance System) generally indicates a technology for improving the convenience and safety of a driver by using a sensor capable of recognizing a peripheral environment while a vehicle is traveling and control devices capable of determining the traveling state of the vehicle and deciding the movement of the vehicle. An ADAS image recognition apparatus recognizes information (a lane, another vehicle, a light source, a pedestrian, and a traffic sign board) on a road, on which a vehicle is traveling, by using an image recognition technology.
Since a traffic sign board has been typically manufactured by drawing a standardized mark having a specific shape on a circular or triangular plate, there have been made efforts to develop a traffic sign board recognition apparatus for recognizing the shape and mark of the traffic sign board by using an image processing technique, to inform a driver of a current traveling environment on a road, and to improve traveling safety and convenience.
Recently, an LED is mainly applied to a traffic sign board in Europe, and is also partially introduced in South Korea. Since a light emitting type sign board is less affected by peripheral illumination and the content of the sign board can be variably displayed or luminance can be changed, it is applied for improvement of visibility at night, traffic, and a change in a limit speed due to weather.
Since the ADAS image recognition apparatus processes a digital image input through a camera by using a numerical analysis technique, its performance may be largely depend on the characteristics of an input image.
In the case of a reflective traffic sign board, since sunlight in the daytime, a street light at night, and headlights of its own vehicle and other vehicles are mainly reflected by the traffic sign board, are incident into a camera of the ADAS image recognition apparatus, and are converted into a digital image, the reflective traffic sign board is largely affected by the brightness or direction of a peripheral light source. Meanwhile, in the case of the light emitting type sign board, since light emitted from its own light source, regardless of other light sources, is incident into a camera of the image recognition apparatus, it is not affected by a peripheral light source. Due to such a difference of characteristics therebetween, it is difficult to capture two types of traffic sign boards so as to be recognized in the same camera.
That is, traffic sign board detection and recognition technologies are developed in order to achieve an intelligent vehicle system capable of performing manless driving, but a technology capable of reliably recognizing both the reflective traffic sign board and the light emitting type sign board is not still proposed in these technologies.